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Slow Coolant Leak

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I have a 2000 996 with 34K miles that has an occasional leak from what appears to be the reservoir cap. I can see crust around the bottom of the cap and around the screw lip on the reservoir (see photo). The coolant appears to be dripping down the overflow hose and onto the driver's side muffler and onto the ground. I have topped off the reservoir and the temperature gauge reads 180 degrees when warm. Is this common?


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I'd like to add one more thing about these overflow reservoir caps, including the .01 rev. If the cap threads and top seal are not lubricated, then the cap will not fully seat, and can cause a leaky cap. The cap should seat with 2 of the "cross ends" 90 degrees to the ground. With an un-lubricated cap, the cap will bind with about an 1/8th to a 1/16th of the way to go, this is enough to let the cap seep or weep out coolant. It is not a whole lot, but is more than what should come out (none!)

I use some spray silicone spray lightly on the cap threads, and on the rubber gasket on the bottom of the inside of the cap. With the silicone on the cap, when the cap is almost fully closed, you will feel the effort to turn the cap increase, then it sorta snaps into the last bit.

My 02 996 has an .01 cap, and it was still weeping out a little coolant.

When I looked at the cap I saw it was off just a bit. So I took off the cap, cleaned off all of the escaped coolant residue and then sprayed on some silicone spray. After that, the cap clicked into place. No leakage so far, so I hope I fixed the root problem.

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I was having a coolant leak with my 2001 996 C4 on the driver's side exhaust tip. I had a '00' part number cap and replaced it with the '01' part number cap. I went for a drive and parked the pcar in the garage. I just went out to get the mail through the garage and noticed I still have a coolant link. The leak does not appear to becoming from the overflow hose coming out of where the cap is located. I had the coolant system pressure checked today when I got the oil changed and it was fine. Any ideas on what is going on?


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Most common cause is the coolant tank is cracked.

I started out with a leaking cap and about a month after I put on the new cap, the coolant tank let go. The coolant tanks are renouned for cracking...but it's really hard to see the crack sometimes....the better pressure retention from the new cap can cause the older coolant tanks to finally let go. I haven't had any more problems since I replaced both.

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Most common cause is the coolant tank is cracked.

Yes! I had this problem yesterday, I parked up in my parking spot and noticed coolant dripping on the near side rear of the car, took the bottle out, a tiny hairline crack, as a temporary fix we applied some epoxy (stuff used with fiberglass), seems to have done the job for the moment.

Will order a new tank on Tuesday, not to hard to change over..

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